The present invention relates to a slide-rocker bearing for bridges or similar structures.
Bearings of this type generally comprise a deformable elastic pressure cushion arranged between an upper bearing member and a lower bearing member. The pressure cushion is peripherally enclosed by a cylindrical casing which is spaced from the bearing members allowing tilting movement under deforming load conditions placed upon one of the bearings. A slide plate of such low friction material as polytetrafluoroethylene (PTFE) is interposed between the upper bearing member and the pressure cushion so as to provide an easily slidable surface for the upper bearing member. A slide-rocker bearing of the above type is shown in German Pat. No. 2,353,733. In the construction shown in this publication the casing is provided with a shoulder which is directed radially inwardly and which is provided with a bore, in which the peripheral edge of a PTFE slide plate is received. Otherwise, the slide plate rests directly upon the elastic pressure cushion. As a result during tilting movements of the bearing, which always lead to eccentricity in the load application, the radially extending internal edge of the bore cuts into the PTFE slide plate, endangering the mounting or encasement of the PTFE sliding plate within the bore itself making it possible for the slide plate to emerge through the gap or space between the casing and the adjacent bearing member. The ability of the slide plate to be further dislodged is increased by the counter deformation energy applied by the pressure cushion itself to the resilient PTFE slide plate. Thus, deformation is frictionally followed by a creeping of the material of the pressure cushion itself into the area of the deformation. This is emperically observed, during tests, as a symptom of tilting movements, occuring in the marginal area of the pressure cushion edge. When heavy bearing loads and large angles of tilt are involved, the known slide rocker bearings may become unsafe and the PTFE slide plate may become completely dislodged.